Dehydrocyclodimerization using uzm-44 aluminosilicate zeolite

ABSTRACT

A process for dehydrocyclodimerization using a catalytic composite comprising at least one of a new family of aluminosilicate zeolites designated UZM-44 has been developed. These zeolites are represented by the empirical formula. 
       Na n M m   k+ T t Al 1-x E x Si y O z    
     where “n” is the mole ratio of Na to (Al+E), M represents a metal or metals from zine, Group 1, Group 2, Group 3 and or the lanthanide series of the periodic table, “m” is the mole ratio of M to (Al+E), “k” is the average charge of the metal or metals M, T is the organic structure directing agent or agents, and E is a framework element such as gallium. UZM-44 has catalytic properties for carrying processes involving contacting at least one aliphatic hydrocarbon having from 2 to about 6 carbon atoms per molecule with the UZM-44 to produce at least one aromatic hydrocarbon.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Provisional Application No.61/736,333 filed Dec. 12, 2012, the contents of which are herebyincorporated by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to a new family of aluminosilicate zeolitesdesignated UZM-44 as the catalytic composite fordehydrocyclodimerization reactions. They are represented by theempirical formula of:

Na_(n)M_(m) ^(k+)T_(t)Al_(1-x)E_(x)Si_(y)O_(z)

where M represents a metal or metals from zinc or Group 1 (IUPAC 1),Group 2 (IUPAC 2), Group 3 (IUPAC 3) or the lanthanide series of theperiodic table, T is the organic directing agent derived from reactantsR and Q where R is an A,Ω-dihalosubstituted alkane such as1,5-dibromopentane and Q is at least one neutral amine having 6 or fewercarbon atoms such as 1-methylpyrrolidine. E is a framework element suchas gallium.

BACKGROUND OF THE INVENTION

Zeolites are crystalline aluminosilicate compositions which aremicroporous and which are formed from corner sharing AlO₂ and SiO₂tetrahedra. Numerous zeolites, both naturally occurring andsynthetically prepared, are used in various industrial processes.Synthetic zeolites are prepared via hydrothermal synthesis employingsuitable sources of Si, Al and structure directing agents such as alkalimetals, alkaline earth metals, amines, or organoammonium cations. Thestructure directing agents reside in the pores of the zeolite and arelargely responsible for the particular structure that is ultimatelyformed. These species balance the framework charge associated withaluminum and can also serve as space fillers. Zeolites are characterizedby having pore openings of uniform dimensions, having a significant ionexchange capacity, and being capable of reversibly desorbing an adsorbedphase which is dispersed throughout the internal voids of the crystalwithout significantly displacing any atoms which make up the permanentzeolite crystal structure. Zeolites can be used as catalysts forhydrocarbon conversion reactions, which can take place on outsidesurfaces as well as on internal surfaces within the pore.

A particular zeolite, IM-5, was first disclosed by Benazzi, et al. in1996 (FR96/12873; WO98/17581) who describe the synthesis of IM-5 fromthe flexible dicationic structure directing agent,1,5-bis(N-methylpyrrolidinium)pentane dibromide or1,6-bis(N-methylpyrrolidinium)hexane dibromide in the presence ofsodium. After the structure of IM-5 was solved by Baerlocher et al.(Science, 2007, 315, 113-6), the International Zeolite StructureCommission gave the code of IMF to this zeolite structure type, seeAtlas of Zeolite Framework Types. The IMF structure type was found tocontain three mutually orthogonal sets of channels in which each channelis defined by a 10-membered ring of tetrahedrally coordinated atoms,however, connectivity in the third dimension is interrupted every 2.5nm, therefore diffusion is somewhat limited. In addition, multipledifferent sizes of 10-membered ring channels exist in the structure.

Applicants have successfully prepared a new family of materialsdesignated UZM-44. The topology of the materials is similar to thatobserved for IM-5. The materials are prepared via the use of a mixtureof simple commercially available structure directing agents, such as1,5-dibromopentane and 1-methylpyrrolidine. UZM-44 may be used as acatalyst in dehydrocyclodimerization reactions where aliphatichydrocarbons containing from 2 to 6 carbon atoms per molecule arereacted over a catalyst to produce a high yield of aromatics andhydrogen, with a light ends byproduct and a C₂-C₄ recycle product.Processes for dehydrocyclodimerization are known and described in detailin U.S. Pat. No. 4,654,455 and U.S. Pat. No. 4,746,763 which areincorporated by reference.

SUMMARY OF THE INVENTION

As stated, the present invention relates to using a new catalyticcomposite comprising a new aluminosilicate zeolite designated UZM-44 ina process for dehydrocyclodimerization. Accordingly, one embodiment ofthe invention uses a material having a three-dimensional framework of atleast AlO₂ and SiO₂ tetrahedral units and an empirical composition inthe as synthesized and anhydrous basis expressed by an empirical formulaof:

Na_(n)M_(m) ^(k+)T_(t)Al_(1-x)E_(x)Si_(y)O_(z)

where “n” is the mole ratio of Na to (Al+E) and has a value fromapproximately 0.05 to 0.5, M represents at least one metal selected fromthe group consisting of zinc, Group 1 (IUPAC 1), Group 2 (IUPAC 2),Group 3 (IUPAC 3), and the lanthanide series of the periodic table, andany combination thereof, “m” is the mole ratio of M to (Al+E) and has avalue from 0 to 0.5, “k” is the average charge of the metal or metals M,T is the organic structure directing agent or agents derived fromreactants R and Q where R is an A,Ω-dihalogen substituted alkane having5 carbon atoms and Q is at least one neutral monoamine having 6 or fewercarbon atoms, “t” is the mole ratio of N from the organic structuredirecting agent or agents to (Al+E) and has a value of from about 0.5 toabout 1.5, E is an element selected from the group consisting ofgallium, iron, boron and combinations thereof, “x” is the mole fractionof E and has a value from 0 to about 1.0, “y” is the mole ratio of Si to(Al+E) and varies from greater than 9 to about 25 and “z” is the moleratio of O to (Al+E) and has a value determined by the equation:

z=(n+k•m+3+40•y)/2

and the zeolite is characterized in that it has the x-ray diffractionpattern having at least the d-spacings and intensities set forth inTable A. The zeolite is thermally stable up to a temperature of greaterthan 600° C. in one embodiment and at least 800° C. in anotherembodiment.

Another embodiment is directed to the dehydrocyclodimerization processusing a second microporous crystalline zeolite, UZM-44-Modified, whichhas a three-dimensional framework of at least AlO₂ and SiO₂ tetrahedralunits and an empirical composition in the hydrogen form expressed by anempirical formula of

M1_(a) ^(N+)Al_((1-x))E_(x)Si_(y′)O_(z″)

where M1 is at least one exchangeable cation selected from the groupconsisting of alkali, alkaline earth metals, rare earth metals, ammoniumion, hydrogen ion and combinations thereof, “a” is the mole ratio ofM1to (Al+E) and varies from about 0.05 to about 50, “N” is the weightedaverage valence of M1 and has a value of about +1 to about +3, E is anelement selected from the group consisting of gallium, iron, boron, andcombinations thereof, x is the mole fraction of E and varies from 0 to1.0, y′ is the mole ratio of Si to (Al+E) and varies from greater thanabout 9 to virtually pure silica and z″ is the mole ratio of O to (Al+E)and has a value determined by the equation:

z″=(a•N+3+4•y′)/2

The zeolite may be characterized in that it has the x-ray diffractionpattern having at least the d-spacings and intensities set forth inTable B. The zeolite is thermally stable up to a temperature of greaterthan 600° C. in one embodiment and at least 800° C. in anotherembodiment.

The zeolite of the catalytic composite used in the process may beprepared by a process comprising forming a reaction mixture containingreactive sources of Na, R, Q, Al, Si and optionally E and/or M andheating the reaction mixture at a temperature of about 160° C. to about180° C., or about 165° C. to about 175° C., for a time sufficient toform the zeolite. The reaction mixture has a composition expressed interms of mole ratios of the oxides of:

a−b Na₂O:bM_(a/2)O:cRO:dQ:1−eAl₂O₃:eE₂O₃:fSiO₂:gH₂O

where “a” has a value of about 10 to about 30, “b” has a value of 0 toabout 30, “c” has a value of about 1 to about 10, “d” has a value ofabout 2 to about 30, “e” has a value of 0 to about 1.0, “f” has a valueof about 30 to about 100, “g” has a value of about 100 to about 4000.With this number of reactive reagent sources, many orders of additioncan be envisioned. Typically, the aluminum reagent is dissolved in thesodium hydroxide prior to adding the silica reagents. Reagents R and Qcan be added together or separately in many different orders ofaddition.

The invention uses UZM-44 as the catalyst or a catalyst component in aprocess of dehydrocyclodimerization using the above-described zeolite asat least a portion of the catalytic composite. The process comprisesreacting aliphatic hydrocarbons containing from 2 to about 6 carbonatoms per molecule over a catalyst to produce a high yield of aromaticsand hydrogen, with a light ends byproduct and a C₂-C₄ recycle product.The dehydrocyclodimerization reaction is carried out at temperatures inexcess of 300° C. (572° F.), using the dual functional catalystcontaining acidic and dehydrogenation components. At least the acidicfunction is provided by the zeolite described above which promotes theoligomerization and aromatization reactions. Optionally, a non-noblemetal component may also be used to promote the dehydrogenationfunction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an XRD pattern of the UZM-44 zeolite formed in Example 1. Thispattern shows the UZM-44 zeolite in the as-synthesized form.

FIG. 2 is also an XRD pattern of the UZM-44 zeolite formed in Example 1.This pattern shows the UZM-44 zeolite in the H⁺ form.

FIG. 3 is a plot derived from the N2 BET experiment where dV/dlog(D) isplotted against the pore diameter. This plot shows the incrementalamount of nitrogen adsorbed at each pore diameter measured.

DETAILED DESCRIPTION OF THE INVENTION

Applicants have prepared a catalytic component suitable for catalyzingdehydrocyclodimerization reactions where the catalytic component is analuminosilicate zeolite whose topological structure is related to IMF asdescribed in Atlas of Zeolite Framework Types, which is maintained bythe International Zeolite Association Structure Commission athttp://www.iza-structure.org/databases/, the member of which has beendesignated IM-5. As will be shown in detail, UZM-44 is different fromIM-5 in a number of its characteristics including its micropore volume.The instant microporous crystalline zeolite, UZM-44, has an empiricalcomposition in the as synthesized and anhydrous basis expressed by anempirical formula of:

Na_(n)M_(m) ^(k+)T_(t)Al_(1-x)E_(x)Si_(y)O_(z)

where “n” is the mole ratio of Na to (Al+E) and has a value fromapproximately 0.05 to 0.5, M represents a metal or metals selected fromthe group consisting of zinc, Group 1 (IUPAC 1), Group 2 (IUPAC 2),Group 3 (IUPAC 3), the lanthanide series of the periodic table, and anycombination thereof, “m” is the mole ratio of M to (Al+E) and has avalue from 0 to 0.5, “k” is the average charge of the metal or metals M,T is the organic structure directing agent or agents derived fromreactants R and Q where R is an A,Ω-dihalogen substituted alkane having5 carbon atoms and Q is at least one neutral monoamine having 6 or fewercarbon atoms, “t” is the mole ratio of N from the organic structuredirecting agent or agents to (Al+E) and has a value of from 0.5 to 1.5,E is an element selected from the group consisting of gallium, iron,boron and combinations thereof, “x” is the mole fraction of E and has avalue from 0 to about 1.0, “y” is the mole ratio of Si to (Al+E) andvaries from greater than 9 to about 25 and “z” is the mole ratio of O to(Al+E) and has a value determined by the equation:

z=(n+k•m+3+4•y)/2

where M is only one metal, then the weighted average valence is thevalence of that one metal, i.e. +1 or +2. However, when more than one Mmetal is present, the total amount of:

M _(m) ^(k+) =M _(m1) ^((k1)+) +M _(m2) ^((k2)+) +M _(m3) ^((k3)+) +M_(m4) ^((k4)+)+ . . .

and the weighted average valence “k” is given by the equation:

$k = \frac{{m\; {1 \cdot k}\; 1} + {m\; {2 \cdot k}\; 2} + {m\; {3 \cdot k}\; 3\mspace{11mu} \ldots}}{{m\; 1} + {m\; 2} + {m\; 3\mspace{11mu} \ldots}}$

In one embodiment, the microporous crystalline zeolite, UZM-44, issynthesized by a hydrothermal crystallization of a reaction mixtureprepared by combining reactive sources of sodium, organic structuredirecting agent or agents T, aluminum, silicon, and optionally E, M, orboth. The reaction mixture does not comprise seeds of a layered materialL. The sources of aluminum include but are not limited to aluminumalkoxides, precipitated aluminas, aluminum metal, aluminum hydroxide,sodium aluminate, aluminum salts and alumina sols. Specific examples ofaluminum alkoxides include, but are not limited to aluminum sec-butoxideand aluminum ortho isopropoxide. Sources of silica include but are notlimited to tetraethylorthosilicate, colloidal silica, precipitatedsilica and alkali silicates. Sources of sodium include but are notlimited to sodium hydroxide, sodium bromide, sodium aluminate, andsodium silicate.

T is the organic structure directing agent or agents derived fromreactants R and Q where R is an A,Ω-dihalogen substituted alkane having5 carbon atoms and Q comprises at least one neutral monoamine having 6or fewer carbon atoms. R may be an AS2-dihalogen substituted alkanehaving 5 carbon atoms selected from the group consisting of1,5-dichloropentane, 1,5-dibromopentane, 1,5-diiodopentane, andcombinations thereof. Q comprises at least one neutral monoamine having6 or fewer carbon atoms such as 1-ethylpyrrolidine, 1-methylpyrrolidine,1-ethylazetidine, 1-methylazetidine, triethylamine, diethylmethylamine,dimethylethylamine, trimethylamine, dimethylbutylamine,dimethylpropylamine, dimethylisopropylamine, methylethylpropylamine,methylethylisopropylamine, dipropylamine, diisopropylamine,cyclopentylamine, methylcyclopentylamine, hexamethyleneimine. Q maycomprise combinations of multiple neutral monoamines having 6 or fewercarbon atoms.

M represents at least one exchangeable cation of a metal or metals fromGroup 1 (IUPAC 1), Group 2 (IUPAC 2), Group 3 (IUPAC 3) or thelanthanide series of the periodic table and or zinc. Specific examplesof M include but are not limited to lithium, potassium, rubidium,cesium, magnesium, calcium, strontium, barium, zinc, yttrium, lanthanum,gadolinium, and mixtures thereof Reactive sources of M include, but arenot limited to, the group consisting of halide, nitrate, sulfate,hydroxide, or acetate salts. E is an element selected from the groupconsisting of gallium, iron, boron and combinations thereof, andsuitable reactive sources include, but are not limited to, boric acid,gallium oxyhydroxide, gallium nitrate, gallium sulfate, ferric nitrate,ferric sulfate, ferric chloride and mixtures thereof.

The reaction mixture containing reactive sources of the desiredcomponents can be described in terms of molar ratios of the oxides bythe formula:

a−b Na₂O:bM_(n/2)O:cRO:dQ:1−eAl₂O₃:eE₂O₃:fSiO₂:gH₂O

where “a” has a value of about 10 to about 30, “b” has a value of 0 toabout 30, “c” has a value of about 1 to about 10, “d” has a value ofabout 2 to about 30, “e” has a value of 0 to about 1.0, “f” has a valueof about 30 to about 100, “g” has a value of about 100 to about 4000.The examples demonstrate specific orders of addition for the reactionmixture which leads to UZM-44. However, as there are at least 6 startingmaterials, many orders of addition are possible. Also, if alkoxides areused, it is preferred to include a distillation or evaporative step toremove the alcohol hydrolysis products. While the organic structuredirecting agents R and Q can be added separately or together to thereaction mixture at a number of points in the process, it is preferredto mix R and Q together at room temperature and add the combined mixtureto a cooled mixture of reactive Si, Al and Na sources maintained at0-10° C. Alternatively, the mixture of R and Q, after mixing at roomtemperature, could be cooled and the reactive sources of Si, Al, and Naadded to the organic structure directing agent mixture while maintaininga temperature of 0-10° C. In an alternative embodiment, the reagents Rand Q could be added, separately or together, to the reaction mixture atroom temperature.

The reaction mixture is then reacted at a temperature of about 160° C.to about 180° C., or about 165° C. to about 175° C., for a period ofabout 1 day to about 3 weeks and preferably for a time of about 3 daysto about 14 days in a stirred, sealed reaction vessel under autogenouspressure. Static crystallization does not yield UZM-44. Aftercrystallization is complete, the solid product is isolated from theheterogeneous mixture by means such as filtration or centrifugation, andthen washed with deionized water and dried in air at ambient temperatureup to about 100° C.

The as-synthesized UZM-44 is characterized by the x-ray diffractionpattern, having at least the d-spacings and relative intensities setforth in Table A below. Diffraction patterns herein were obtained usinga typical laboratory powder diffractometer, utilizing the K_(α) line ofcopper; Cu K alpha. From the position of the diffraction peaksrepresented by the angle 2theta, the characteristic interplanardistances d_(hkl) of the sample can be calculated using the Braggequation. The intensity is calculated on the basis of a relativeintensity scale attributing a value of 100 to the line representing thestrongest peak on the X-ray diffraction pattern, and then: very weak(vw) means less than 5; weak (w) means less than 15; medium (m) means inthe range 15 to 50; strong (s) means in the range 50 to 80; very strong(vs) means more than 80. Intensities may also be shown as inclusiveranges of the above. The X-ray diffraction patterns from which the data(d spacing and intensity) are obtained are characterized by a largenumber of reflections some of which are broad peaks or peaks which formshoulders on peaks of higher intensity. Some or all of the shoulders maynot be resolved. This may be the case for samples of low crystallinity,of particular coherently grown composite structures or for samples withcrystals which are small enough to cause significant broadening of theX-rays. This can also be the case when the equipment or operatingconditions used to produce the diffraction pattern differ significantlyfrom those used in the present case.

The X-ray diffraction pattern for UZM-44 contains many peaks, an exampleof the x-ray diffraction patterns for an as-synthesized UZM-44 productis shown in FIG. 1. Those peaks characteristic of UZM-44 are shown inTable A. Additional peaks, particularly those of very weak intensity,may also be present. All peaks of medium or higher intensity present inUZM-44 are represented in Table A.

The zeolite may be further characterized by the x-ray diffractionpattern having at least the d-spacings and intensities set forth inTable A.

TABLE A 2-Theta d(†) I/Io % 7.72 11.45 m 8.88 9.95 m 9.33 9.47 m 12.477.09 w-m 12.85 6.88 vw 14.62 6.05 vw-w 15.27 5.80 w 15.57 5.68 w 16.605.34 w 17.70 5.01 vw-w 18.71 4.74 w-m 19.30 4.59 w 22.55 3.94 m 23.033.86 vs 23.39 3.80 s 24.17 3.68 m 25.01 3.56 m 26.19 3.40 vw-w 26.683.34 w-m 28.76 3.10 w-m 30.07 2.97 w 35.72 2.51 vw-w 45.08 2.01 w 45.831.98 vw-w 46.77 1.94 vw-w

As will be shown in detail in the examples, the UZM-44 material isthermally stable up to a temperature of at least 600° C. and in anotherembodiment, up to at least 800° C. Also as shown in the examples, theUZM-44 material may have a micropore volume as a percentage of totalpore volume of less than 60%.

Characterization of the UZM-44 product by high-resolution scanningelectron microscopy shows that the UZM-44 forms in lathes which assembleinto rectangular rod colonies.

As synthesized, the UZM-44 material will contain some exchangeable orcharge balancing cations in its pores. These exchangeable cations can beexchanged for other cations, or in the case of organic cations, they canbe removed by heating under controlled conditions. It is also possibleto remove some organic cations from the UZM-44 zeolite directly by ionexchange. The UZM-44 zeolite may be modified in many ways to tailor itfor use in a particular application. Modifications include calcination,ion-exchange, steaming, various acid extractions, ammoniumhexafluorosilicate treatment, or any combination thereof, as outlinedfor the case of UZM-4M in U.S. Pat. No. 6,776,975 B1 which isincorporated by reference in its entirety. Conditions may be more severethan shown in U.S. Pat. No. 6,776,975. Properties that are modifiedinclude porosity, adsorption, Si/Al ratio, acidity, thermal stability,and the like.

After calcination, ion-exchange and calcination and on an anhydrousbasis, the microporous crystalline zeolite UZM-44 has athree-dimensional framework of at least AlO₂ and SiO₂ tetrahedral unitsand an empirical composition in the hydrogen form expressed by anempirical formula of

M1_(a) ^(N+)Al_((1-x))E_(x)Si_(y′)O_(z″)

where M1 is at least one exchangeable cation selected from the groupconsisting of alkali, alkaline earth metals, rare earth metals, ammoniumion, hydrogen ion and combinations thereof, “a” is the mole ratio of M1to (Al+E) and varies from about 0.05 to about 50, “N” is the weightedaverage valence of M1 and has a value of about +1 to about +3, E is anelement selected from the group consisting of gallium, iron, boron, andcombinations thereof, x is the mole fraction of E and varies from 0 to1.0, y′ is the mole ratio of Si to (Al+E) and varies from greater thanabout 9 to virtually pure silica and z″ is the mole ratio of O to (Al+E)and has a value determined by the equation:

z″=(a•N+3+4•y′)/2

In the hydrogen form, after calcination, ion-exchange and calcination toremove NH₃, UZM-44 displays the x-ray diffraction pattern having atleast the d-spacings and intensities set forth in Table B. Those peakscharacteristic of UZM-44 are shown in Tables B. Additional peaks,particularly those of very weak intensity, may also be present. Allpeaks of medium or higher intensity present in UZM-44 in Table B.

TABLE B 2-Theta d(†) I/Io % 7.71 11.47 m-s 8.84 10.00 m-s 9.24 9.56 m11.76 7.52 vw-w 12.46 7.10 m 14.38 6.15 vw 14.64 6.05 w 15.26 5.80 w15.52 5.70 w-m 16.58 5.34 w 17.72 5.00 w-m 18.64 4.76 w 22.56 3.94 w-m23.06 3.85 vs 23.40 3.80 s 24.12 3.69 m 25.06 3.55 m 26.16 3.40 vw-w26.74 3.33 w-m 28.82 3.10 w-m 30.12 2.96 w 35.86 2.50 vw-w 45.32 2.00 w46.05 1.97 vw-w 46.92 1.93 vw-w

Similar to the as-synthesized material, the modified UZM-44 materialsare thermally stable up to a temperature of at least 600° C. and inanother embodiment, up to at least 800° C. and may have a microporevolume as a percentage of total pore volume of less than 60%.

Surface area, micropore volume and total pore volume may be determined,for example, by N₂ adsorption using the conventional BET method ofanalysis (J. Am. Chem. Soc., 1938, 60, 309-16) coupled with t-plotanalysis of the adsorption isotherm as implemented in Micromeritics ASAP2010 software. The t-plot is a mathematical representation ofmulti-layer adsorption and allows determination of the amount of N₂adsorbed in the micropores of the zeolitic material under analysis. Inparticular, for the materials described herein, points at 0.45, 0.50,0.55, 0.60, and 0.65 P/P₀ are used to determine the slope of the t-plotline, the intercept of which is the micropore volume. Total pore volumeis determined at 0.98 P/P₀. The UZM-44 of the instant invention has amicropore volume of less than 0.155 mL/g, typically less than 0.15 andoften less than 0.145 mL/g. Additionally, by looking at the dV/dlog Dversus pore diameter plot (the differential volume of nitrogen adsorbedas a function of pore diameter), as shown in FIG. 3, the UZM-44 of theinstant invention contains no feature at around 200-300 Å, where theExample 2 material does and instead have adsorption occurring at greaterthan 450 Å, where greater than 0.1 mL N₂/gA is differentially adsorbedat a pore diameter of 475 Å. Preferably, greater than 0.1 mL N₂/gA isdifferentially adsorbed at a pore diameters greater than 475 Å wheredifferentially adsorbed indicates the differential volume of nitrogenadsorbed at a particular pore diameter.

By virtually pure silica is meant that virtually all the aluminum and/orthe E metals have been removed from the framework. It is well known thatit is virtually impossible to remove all the aluminum and/or E metal.Numerically, a zeolite is virtually pure silica when y′ has a value ofat least 3,000, preferably 10,000 and most preferably 20,000. Thus,ranges for y′ are from 9 to 3,000; from greater than 20 to about 3,000;from 9 to 10,000; from greater than 20 to about 10,000; from 9 to20,000; and from greater than 20 to about 20,000.

In specifying the proportions of the zeolite starting material oradsorption properties of the zeolite product and the like herein, the“anhydrous state” of the zeolite will be intended unless otherwisestated. The term “anhydrous state” is employed herein to refer to azeolite substantially devoid of both physically adsorbed and chemicallyadsorbed water.

The UZM-44 zeolite is employed as at least a portion of a catalyst in adehydrocyclodimerization process for preparing an aromatic stream from alight aliphatic hydrocarbon stream. The process uses adehydrocyclodimerization catalyst which comprises the UZM-44 zeolitecomponent, optionally a binder component, and optionally a metalcomponent. The metal component may be a metal such as gallium to promotethe dehydrogenation function. The gallium component may be incorporatedinto the catalytic composite in any suitable manner known to the artwhich results in a uniform dispersion of the gallium such as byion-exchange, cogelation, or impregnation either after, before, orduring the compositing of the catalyst formulation. Usually the galliumis deposited onto the catalyst by impregnating the catalyst with a saltof the gallium metal. The particles are impregnated with using galliummetal or gallium containing compounds such as gallium oxyhydroxide,gallium nitrate, gallium chloride, gallium bromide, gallium sulfate,gallium acetate, and gallium oxide. The amount of gallium which isdeposited onto the catalyst varies from about 0.1 to about 5 weightpercent of the finished catalyst expressed as the metal. The galliumcompound may be impregnated onto the support particles by any techniquewell known in the art such as dipping the catalyst into a solution ofthe metal compound or spraying the solution onto the support. One methodof preparation involves the use of a steam jacketed rotary dryer. Thesupport particles are immersed in the impregnating solution contained inthe dryer and the support particles are tumbled therein by the rotatingmotion of the dryer. Evaporation of the solution in contact with thetumbling support is expedited by applying steam to the dryer jacket.Following drying, the gallium impregnated catalyst may then be calcinedto convert the gallium to the oxide phase. An exemplary method forperforming the gallium incorporation step is disclosed in U.S. Pat. No.6,657,096, hereby incorporated by reference.

The zeolite as outlined above, or a modification thereof, may be in acomposite with commonly known binders. The UZM-44 is used as a catalystor catalyst support in various reactions. The UZM-44 preferably is mixedwith a binder for convenient formation of catalyst particles in aproportion of about 5 to 100 mass % UZM-44 zeolite and 0 to 95 mass-%binder, with the UZM-44 zeolite preferably comprising from about 10 to90 mass-% of the composite. The binder should preferably be porous, havea surface area of about 5 to about 800 m²/g, and be relativelyrefractory to the conditions utilized in the hydrocarbon conversionprocess. Non-limiting examples of binders are alumina, titania,zirconia, zinc oxide, magnesia, boria, silica-alumina, silica-magnesia,chromia-alumina, alumina-boria, aluminophosphates, silica-zirconia,silica, silica gel, and clays. Preferred binders are aluminophosphates,amorphous silica and alumina, including gamma-, eta-, and theta-alumina,with aluminophosphates being especially preferred.

The zeolite with or without a binder can be formed into various shapessuch as pills, pellets, extrudates, spheres, etc. Preferred shapes areextrudates and spheres. Extrudates are prepared by conventional meanswhich involves mixing of the composition either before or after addingmetallic components, with the binder and a suitable peptizing agent toform a homogeneous dough or thick paste having the correct moisturecontent to allow for the formation of extrudates with acceptableintegrity to withstand direct calcination. The dough then is extrudedthrough a die to give the shaped extrudate. A multitude of differentextrudate shapes are possible, including, but not limited to, cylinders,cloverleaf, dumbbell and symmetrical and asymmetrical polylobates. It isalso within the scope of this invention that the extrudates may befurther shaped to any desired form, such as spheres, by any means knownto the art.

Spheres can be prepared by the well known oil-drop method which isdescribed in U.S. Pat. No. 2,620,314 which is incorporated by reference.The method involves dropping a mixture of zeolite, and for example,alumina sol, and gelling agent into an oil bath maintained at elevatedtemperatures. The droplets of the mixture remain in the oil bath untilthey set and form hydrogel spheres. The spheres are then continuouslywithdrawn from the oil bath and typically subjected to specific agingtreatments in oil and an ammoniacal solution to further improve theirphysical characteristics. The resulting aged and gelled particles arethen washed and dried at a relatively low temperature of about 50 toabout 200° C. and subjected to a calcination procedure at a temperatureof about 450 to about 700° C. for a period of about 1 to about 20 hours.This treatment effects conversion of the hydrogel to the correspondingoxide or phosphate matrix.

The dehydrocyclodimerization conditions which are employed varydepending on such factors as feedstock composition and desiredconversion. A desired range of conditions for thedehydrocyclodimerization of C₂-C₆ aliphatic hydrocarbons to aromaticsinclude a temperature from about 350° C. to about 650° C. (662° F. to1202° F.), a pressure from about 0 to about 300 psi(g) (0 to 2068kPa(g)), and a liquid hourly space velocity from about 0.2 to about 5hr⁻¹. One embodiment of the invention employs process conditionsincluding a temperature in the range from about 400° C. to about 600° C.(752° F. to 1112° F.), a pressure in or about the range from about 0 toabout 150 psi(g) (0 to 1034 kPa(g)), and a liquid hourly space velocityof between 0.5 to 3.0 hr⁻¹. It is understood that, as the average carbonnumber of the feed increases, a temperature in the lower end of thetemperature range is required for optimum performance and conversely, asthe average carbon number of the feed decreases, the higher the requiredtemperature.

The feed stream to the dehydrocyclodimerization process is definedherein as all streams introduced into the dehydrocyclodimerizationreaction zone. Included in the feed stream is the at least one aliphatichydrocarbon having from 2 to about 6 carbon atoms. The feed stream isreferred to as comprising C₂-C₆ aliphatic hydrocarbons. By C₂-C₆aliphatic hydrocarbons is meant one or more open, straight or branchedchain isomers having from two to six carbon atoms per molecule.Furthermore, the hydrocarbons in the feedstock may be saturated orunsaturated. Preferably, the hydrocarbons are C₃'s and/or C₄'s selectedfrom isobutane, normal butane, isobutene, normal butene, propane andpropylene. Examples of potential feed streams include C₃ and/or C₄derived streams from FCC cracked products, light gasses from a delayedcoking process, and liquefied petroleum gas streams (LPG). Diluents mayalso be included in the feed stream. Examples of such diluents includewater, nitrogen, helium, argon, neon. Aromatic products generated by thedehydrocyclodimerization process may include benzene, toluene, xylenes,aromatics with 9 or 10 carbon atoms, and mixtures thereof. In oneembodiment, the aromatic products include benzene, toluene, and xylenes.The aromatic products may be used as reactants in later refining orpetrochemical processes.

Molecular hydrogen is produced in a dehydrocyclodimerization reaction aswell as aromatic hydrocarbons. For example, reacting a C₄ paraffin willyield 5 moles of hydrogen for every one mole of aromatic produced.Because the equilibrium concentration of aromatics is inverselyproportional to the fifth power of the hydrogen concentration, it isdesired to carry out the reaction in the absence of added hydrogen.Adherence to this practice, however, promotes catalyst deactivation and,as a result, short catalyst life before regeneration. The rapiddeactivation is believed to be caused by excessive carbon formation(coking) on the catalyst surface. This coking tendency makes itnecessary to relatively frequently perform catalyst regeneration.Reducing the deactivation occurring during successive regenerationsrequires a hydrothermally stable zeolite, that is, a zeolite for whichsurface area, micropore volume and/or tetrahedral Al content are stableafter exposure to high temperatures and steam quantities. The catalystused in this dehydrocyclodimerization has the advantage of hydrothermalstability which may lead to longer catalyst life.

The catalyst may be in a fixed bed system, a moving bed system, afluidized bed system, or in a batch type operation; however, in view ofthe danger of attrition losses of the valuable catalyst and of thewell-known operational advantages, it is preferred to use either a fixedbed system or a dense-phase moving bed system.

In a fixed bed system or a dense-phase moving bed system, the feedstream is preheated by any suitable heating means to the desiredreaction temperature and then passed into a dehydrocyclodimerizationzone containing a bed of catalyst. It is understood that thedehydrocyclodimerization zone may be one or more separate reactors withsuitable means between separate reactors if any to compensate for anyendothermicity encountered in each reactor and to assure that thedesired temperature is maintained at the entrance to each reactor. It isalso important to note that the feed stream may be contacted with thecatalyst bed in either upward, downward, or radial flow fashion with thelatter being preferred. In addition, the feed stream is in the vaporphase when its' components contact the catalyst bed. Each reactor maycontain one or more fixed or dense-phase moving beds of catalyst.

The dehydrocyclodimerization system may comprise adehydrocyclodimerization zone containing one or more reactors and/orbeds of catalyst. In a multiple bed system, it is, of course, within thescope of the present invention to use one catalyst in less than all ofthe beds with another dehydrocyclodimerization or similarly behavingcatalyst being used in the remainder of the beds. Specific to thedense-phase moving bed system, it is common practice to remove catalystfrom the bottom of a reactor in the dehydrocyclodimerization zone,regenerate it by conventional means known to the art, and then return itto the top of that reactor or another reactor in thedehydrocyclodimerization zone. The reactor or reactors utilized in theprocess may be linked to a product recovery system in various mannersdescribed in the prior art to achieve specific desired results. U.S.Pat. No. 4,642,402 for example discloses a method of combining areaction zone and product recovery zone to optimize the xylene producedin a dehydrocyclodimerization process. The product recovery section mayrecover streams such as hydrogen, light hydrocarbons, and benzene. In anembodiment, at least a portion of a light hydrocarbon stream comprisingC₂-C₆ hydrocarbons is recycled to the dehydrocyclodimerization zone as aportion of the feedstream. In another an embodiment, at least a portionof the benzene stream is recycled to the dehydrocyclodimerization zoneas a portion of the feedstream

After some time on stream (several days to a year), the catalystdescribed above will have lost enough activity due to coking andhydrogen exposure so that it must be reactivated. It is believed thatthe exact amount of time which a catalyst can operate withoutnecessitating regeneration or reactivation will depend on a number offactors. One factor, as is demonstrated herein is whether water is addedto the feed stream.

When the catalyst requires regeneration, typically oxidation or burningof catalyst deactivating carbonaceous deposits with oxygen or anoxygen-containing gas is used. Catalyst regeneration techniques are wellknown and not discussed in detail here. Examples include U.S. Pat. No.4,795,845 (hereby incorporated by reference) which discloses burning thecoke accumulated upon the deactivated catalyst at catalyst regenerationconditions in the presence of an oxygen-containing gas, and U.S. Pat.No. 4,724,271 (hereby incorporated by reference) which additionallydiscloses water removal steps in the catalyst regeneration procedure.The regeneration may proceed in one or multiple burns. For example,there may be a main burn followed by a clean-up burn. The main burnconstitutes the principal portion of the regeneration process with theclean-up burn gradually increasing the amount of molecular oxygen in thegas introduced to the regeneration catalyst until the end of theclean-up burn which is indicated by a gradual decline in the temperatureat the edit of the catalyst bed until the inlet and outlet temperaturesof the catalyst bed merges.

In addition to deactivation by coking requiring regeneration,dehydrocyclodimerization catalysts can be deactivated by exposure tohydrogen at high temperatures and then require reactivation. Similarly,when the catalyst requires reactivation, it is removed from theoperating reactor and contacted with fluid water. Suitable reactivationprocesses are known and not discussed in detail here. One example isU.S. Pat. No. 6,395,664. Using procedures in the art, the catalyst canbe reactivated multiple times. Thus, the catalyst can be hydrogendeactivated, then reactivated, then hydrogen deactivated again, thenreactivated again and so forth. No limit on the number of times that aparticular catalyst can be deactivated and subsequently reactivated isknown. The application and use of additional required items are wellwithin the purview of a person of ordinary skill in the art. U.S. Pat.No. 3,652,231; U.S. Pat. No. 3,647,680; and U.S. Pat. No. 3,692,496;which are incorporated by reference into this document, may be consultedfor additional detailed information.

The following examples are presented in illustration of this inventionand are not intended as undue limitations on the generally broad scopeof the invention as set out in the appended claims.

The structure of the UZM-44 zeolite of this invention was determined byx-ray analysis. The x-ray patterns presented in the following exampleswere obtained using standard x-ray powder diffraction techniques. Theradiation source was a high-intensity, x-ray tube operated at 45 kV and35 ma. The diffraction pattern from the copper K-alpha radiation wasobtained by appropriate computer based techniques. Flat compressedpowder samples were continuously scanned at 2° to 56° (20). Interplanarspacings (d) in Angstrom units were obtained from the position of thediffraction peaks expressed as θ where θ is the Bragg angle as observedfrom digitized data. Intensities were determined from the integratedarea of diffraction peaks after subtracting background, “I_(o)” beingthe intensity of the strongest line or peak, and “I” being the intensityof each of the other peaks.

As will be understood by those skilled in the art the determination ofthe parameter 2θ is subject to both human and mechanical error, which incombination can impose an uncertainty of about ±0.4° on each reportedvalue of 2θ. This uncertainty is, of course, also manifested in thereported values of the d-spacings, which are calculated from the 2θvalues. This imprecision is general throughout the art and is notsufficient to preclude the differentiation of the present crystallinematerials from each other and from the compositions of the prior art. Insome of the x-ray patterns reported, the relative intensities of thed-spacings are indicated by the notations vs, s, m, w and vw whichrepresent very strong, strong, medium, weak, and very weak respectively.In terms of 100 x I/I_(o), the above designations are defined as:

vw=<5; w=6-15; m=16-50: s=51-80; and vs=80-100

In certain instances the purity of a synthesized product may be assessedwith reference to its x-ray powder diffraction pattern. Thus, forexample, if a sample is stated to be pure, it is intended only that thex-ray pattern of the sample is free of lines attributable to crystallineimpurities, not that there are no amorphous materials present.

In order to more fully illustrate the invention, the following examplesare set forth. It is to be understood that the examples are only by wayof illustration and are not intended as an undue limitation on the broadscope of the invention as set forth in the appended claims.

Example 1

5.28 g of NaOH, (97%) was dissolved in 111.88 g water. 1.16 g Al(OH)₃,(29.32 wt.-% Al), was added to the sodium hydroxide solution. Upon themixture becoming a solution, 33.75 g Ludox AS-40 was added and thesolution was stirred vigorously for 1-2 hours and then cooled to 0°C.-4° C. Separately, 8.89 g 1,5-dibromopentane, (97%) was mixed with9.56 g 1-methylpyrrolidine, (97%) to form a second mixture. The secondmixture was added to the cooled mixture to create the final reactionmixture. The final reaction mixture was vigorously stirred andtransferred to a 300 cc stirred autoclave. The final reaction mixturewas digested at 170° C. for 120 hours with stirring at 100 rpm. Theproduct was isolated by filtration. The product was identified as UZM-44by XRD. Analytical results showed this material to have the followingmolar ratios, Si/Al of 11.77, Na/Al of 0.21, N/Al of 1.02, C/N of 7.75.The product generated by this synthesis was calcined under flowing airat 600° for 6 hours. It was then ion exchanged four times with 1 Mammonium nitrate solution at 75° C. followed by a calcination at 500° C.under air for 2 hours to convert NH₄ ⁺ into H⁺. Analysis for thecalcined, ion-exchanged ample shows 39.1% Si, 3.26% Al, 90 ppm Na with aBET surface area of 299 m²/g, pore volume of 0.239 cm3/g, and microporevolume of 0.139 cm3/g.

Comparative Example 2

10.8 g of Aerosil 200 was added, while stirring, to a solution of 12.24g 1,5-bis(N-methylpyrrolidinium)pentane dibromide in 114 g H₂O. A verythick gel was formed. Separately, a solution was made from 60 g H₂O,3.69 g NaOH (99%), 0.95 g sodium aluminate (26.1% Al by analysis), and1.86 g NaBr (99%). This second solution was added to the above mixture.The final mixture was divided equally between 7 45 cc Parr vessels. Onevessel, which was digested for 12 days at 170° C. in a rotisserie ovenat 15 rpm, yielded a product which was determined by XRD as having theIMF structure. The product was isolated by filtration. Analyticalresults showed this material to have the following molar ratios, Si/Alof 12.12, Na/Al of 0.08, N/Al of 1.03, C/N of 7.43. The productgenerated by this synthesis was calcined under flowing air at 600° for 6hours. It was then ion exchanged four times with 1 M ammonium nitratesolution at 75° C. followed by a calcination at 500° C. under air for 2hours to convert NH₄ ⁺ into H⁺. Analysis for the calcined, ion-exchangedsample shows 38.8% Si, 2.99% Al, 190 ppm Na with a BET surface area of340 m²/g, pore volume of 0.260 cm³/g, and micropore volume of 0.160cm³/g.

Example 3

The final reaction mixture was vigorously stirred and transferred to a 5gallon stirred autoclave. The product was isolated by filtration. Theproduct was identified as UZM-44 by XRD. Analytical results showed thismaterial to have the following molar ratios, Si/Al of 11.77, Na/Al of0.21, N/Al of 1.02, C/N of 7.75. The product generated by this synthesiswas calcined under flowing air at 600° for 6 hours. Analysis for thecalcined sample shows a BET surface area of 301 m²/g, pore volume of0.238 cm³/g, and micropore volume of 0.142 cm³/g.

Example 4

A UZM-44 in the H+ form was loaded into a vertical steamer. The UZM-44was exposed to 100% steam at 725° C. for 12 hours or 24 hours. Thestarting UZM-44 had a BET surface area of 340 m²/g, pore volume of 0.301cm³/g, and micropore volume of 0.154 cm³/g. After 12 hours of steaming,the UZM-44 was still identified as UZM-44 by XRD though the intensity ofthe first 3 peaks had increased to very strong, very strong—strong, andvery strong—strong respectively. All other peaks were at positions andintensities described in Table B. The material had a BET surface area of274 m²/g, pore volume of 0.257 cm³/g, and micropore volume of 0.127cm³/g. After 24 hours of steaming, the UZM-44 was still identified asUZM-44 by XRD though the intensity of the first 3 peaks had increased tovery strong, very strong—strong, and very strong—strong respectively.All other peaks were at positions and intensities described in Table B.The material had a BET surface area of 276 m²/g, pore volume of 0.262cm³/g, and micropore volume of 0.128 cm³/g. The UZM-44 demonstrated highhydrothermal stability.

Example 5

The product generated by the synthesis described in Example 1 was boundwith Al₂O₃ in a 75:25 weight ratio and extruded in ⅛″ cylinders to formUZM-44/Al₂O₃. The extrudates were then calcined using a 2° C./minuteramp to 550° C., holding for 3 hours and then cooling to roomtemperature. The 20 to 60 mesh fraction was isolated and then used asthe catalytic composite in a chemical reaction to form ethylbenzene andxylenes.

Benzene and propane were fed at a 2:1 mole ratio into a reactor at 400psig along with a hydrogen stream such that the hydrogen to hydrocarbonmole ratio was about 1.0. At 500° C. and 2.5 WHSV, conversion of benzenewas 63 wt % and conversion of propane was 90 wt %. Yield of aromaticcompounds at these conditions included 25 wt % to toluene, 1 wt % toethylbenzene, 7 wt % to xylenes and 5 wt % to C9 aromatics.

1. A process for dehydrocyclodimerization comprising contacting a feedcomprising at least one aliphatic hydrocarbon having from 2 to about 6carbon atoms per molecule with a microporous crystalline zeoliticcatalytic composite at dehydrocyclodimerization conditions to produce aproduct stream comprising at least one aromatic hydrocarbon wherein thecatalytic composite is selected from the group consisting of a. a firstmicroporous crystalline zeolite, UZM-44, having a three-dimensionalframework of at least AlO₂ and SiO₂ tetrahedral units and an empiricalcomposition in the as synthesized and anhydrous basis expressed by anempirical formula of:Na_(n)M_(m) ^(k+)T_(t)Al_(i-x)E_(x)Si_(y)O_(z) where “n” is the moleratio of Na to (Al+E) and has a value from approximately 0.05 to 0.5, Mrepresents a metal or metals selected from the group consisting of zinc,Group 1 (IUPAC 1), Group 2 (IUPAC 2), Group 3 (IUPAC 3), the lanthanideseries of the periodic table, and any combination thereof, “m” is themole ratio of M to (Al+E) and has a value from 0 to 0.5, “k” is theaverage charge of the metal or metals M, T is the organic structuredirecting agent or agents derived from reactants R and Q where R is anA,Ω-dihalogen substituted alkane having 5 carbon atoms and Q is at leastone neutral monoamine having 6 or fewer carbon atoms, “t” is the moleratio of N from the organic structure directing agent or agents to(Al+E) and has a value of from 0.5 to 1.5, E is an element selected fromthe group consisting of gallium, iron, boron and combinations thereof,“x” is the mole fraction of E and has a value from 0 to about 1.0, “y”is the mole ratio of Si to (Al+E) and varies from greater than 9 toabout 25 and “z” is the mole ratio of 0 to (Al+E) and has a valuedetermined by the equation:z=(n+k•m+3+40•y)/2 b. a second microporous crystalline zeolite,UZM-44-Modified, having a three-dimensional framework of at least AlO₂and SiO₂ tetrahedral units and an empirical composition in the hydrogenform expressed by an empirical formula ofM1_(a) ^(N+)Al_((1-x))E_(x)Si_(y′), O_(z″) where M1 is at least oneexchangeable cation selected from the group consisting of alkali,alkaline earth metals, rare earth metals, ammonium ion, hydrogen ion andcombinations thereof, “a” is the mole ratio of M1 to (Al+E) and variesfrom about 0.05 to about 50, “N” is the weighted average valence of M1and has a value of about +1 to about +3, E is an element selected fromthe group consisting of gallium, iron, boron, and combinations thereof,x is the mole fraction of E and varies from 0 to 1.0, y′ is the moleratio of Si to (Al+E) and varies from greater than about 9 to virtuallypure silica and z″ is the mole ratio of O to (Al+E) and has a valuedetermined by the equation:z″=(a•N+3+4•y′)/2 and c. combinations thereof.
 2. The process of claim 1wherein the first microporous crystalline zeolite, UZM-44, is furthercharacterized in that it has the x-ray diffraction pattern having atleast the d-spacings and intensities set forth in Table A: TABLE A2-Theta d(†) I/Io % 7.72 11.45 m 8.88 9.95 m 9.33 9.47 m 12.47 7.09 w-m12.85 6.88 vw 14.62 6.05 vw-w 15.27 5.80 w 15.57 5.68 w 16.60 5.34 w17.70 5.01 vw-w 18.71 4.74 w-m 19.30 4.59 w 22.55 3.94 m 23.03 3.86 vs23.39 3.80 s 24.17 3.68 m 25.01 3.56 m 26.19 3.40 vw-w 26.68 3.34 w-m28.76 3.10 w-m 30.07 2.97 w 35.72 2.51 vw-w 45.08 2.01 w 45.83 1.98 vw-w46.77 1.94 vw-w


3. The process of claim 1 wherein the second microporous crystallinezeolite, UZM-44-Modified, is further characterized in that it has thex-ray diffraction pattern having at least the d-spacings and intensitiesset forth in Table B: TABLE B 2-Theta d(†) I/Io % 7.71 11.47 m-s 8.8410.00 m-s 9.24 9.56 m 11.76 7.52 vw-w 12.46 7.10 m 14.38 6.15 vw 14.646.05 w 15.26 5.80 w 15.52 5.70 w-m 16.58 5.34 w 17.72 5.00 w-m 18.644.76 w 22.56 3.94 w-m 23.06 3.85 vs 23.40 3.80 s 24.12 3.69 m 25.06 3.55m 26.16 3.40 vw-w 26.74 3.33 w-m 28.82 3.10 w-m 30.12 2.96 w 35.86 2.50vw-w 45.32 2.00 w 46.05 1.97 vw-w 46.92 1.93 vw-w


4. The process of claim 1 wherein the microporous crystalline zeoliticcatalytic composite is thermally stable up to a temperature of greaterthan 600° C.
 5. The process of claim 1 wherein the microporouscrystalline zeolitic catalytic composite has a micropore volume as apercentage of total pore volume of less than 60%.
 6. The process ofclaim 1 wherein the microporous crystalline zeolitic catalytic compositehas a micropore volume of less than 0.155 mL/g
 7. The process of claim 1wherein the microporous crystalline zeolitic catalytic composite has amicropore volume of less than 0.150 mL/g.
 8. The process of claim 1wherein the microporous crystalline zeolitic catalytic compositeexhibits no feature at 200-300 Å on a dV/dlog D versus pore diameterplot of differential volume of nitrogen adsorbed as a function of porediameter.
 9. The process of claim 1 wherein the microporous crystallinezeolitic catalytic composite exhibits adsorption occurring at greaterthan 450 Å on a dV/dlog D versus pore diameter plot of differentialvolume of nitrogen adsorbed as a function of pore diameter.
 10. Theprocess of claim 1 wherein the differential volume of nitrogen adsorbedby the zeolite at a pore diameter of 475A is greater than 0.1 mL N₂/gÅon a dV/dlog D versus pore diameter plot of differential volume ofnitrogen adsorbed as a function of pore diameter.
 11. The process ofclaim 1 wherein the differential volume of nitrogen adsorbed by thezeolite at pore diameters greater than 475 Å is greater than 0.1 mLN₂/gÅ on a dV/dlog D versus pore diameter plot of differential volume ofnitrogen adsorbed as a function of pore diameter.
 12. The process ofclaim 1 wherein the dehydrocyclodimerization conditions include atemperature from about 350° C. to about 650° C. (662° F. to 1202° F.), apressure from about 0 to about 300 psi(g) (0 to 2068 kPa(g)), and aliquid hourly space velocity from about 0.2 to about 5 hr⁻¹.
 13. Theprocess of claim 1 wherein the catalytic composite further comprisesgallium and a binder.
 14. The process of claim 1 wherein thedehydrocyclodimerization conditions include a temperature in the rangefrom about 400° C. to about 600° C. (752° F. to 1112° F.), a pressure inor about the range from about 0 to about 150 psi(g) (0 to 1034 kPa(g)),and a liquid hourly space velocity of between 0.5 to 3.0 hr⁻¹.
 15. Theprocess of claim 1 wherein the catalytic composite is located in one ormore catalyst zones arranged in series or parallel configuration, andwherein the catalytic composite may be in fixed beds or fluidized beds.16. The process of claim 1 wherein the at least one aromatic hydrocarbonis benzene, toluene, or a xylene.
 17. The process of claim 1 wherein thefeed is selected from the group consisting of C₃ and/or C₄ derivedstreams from FCC cracked products, light gasses from a delayed cokingprocess, and liquefied petroleum gas streams.
 18. The process of claim 1wherein the process is operated in a fixed bed or dense-phase mode. 19.The process of claim 1 wherein the product stream further compriseslight hydrocarbons which are separated from the product stream andrecycled to the contacting with a catalytic composite step.
 20. Theprocess of claim 1 wherein the product stream comprises benzene andxylenes the process further comprising separating the benzene andrecycling the separated benzene to the contacting with a catalyticcomposite step.